The Reds have won just one of their last seven games in all competitions, with several defensive errors costing them dearly during that run.
However, Keegan has leapt to the defence of his former side, claiming the Merseysiders are just one of a number of top-flight clubs who are unconvincing defensively.
"There are a lot of teams in the Premier League struggling in defence,” said Keegan at an Aspire Academy event. “All the rules have been changed to suit attackers -- yellow cards, red cards.
"It's no fun being a defender. If a defender misses three tackles he's off so it's no wonder they are cautious.
"I don't think Manchester City, Manchester United or Chelsea are great defensively. It's not just a Liverpool problem.
"Nowadays everything is built for teams to go forward, which is great. Who shows highlights of defending?
"Yes they are conceding goals and they say it's a bit like my [Newcastle] team, but at Liverpool fans want to see a good game of football and they want the team to have a go.”
United and City have both conceded just two goals apiece in their opening seven league games, whereas Liverpool have shipped 12 so far.
Liverpool take on joint-leaders United in the Premier League on Saturday 14 October at Anfield.